You can make changes to the setup and configuration of your Forms at any time.
First open up the Forms tab in the top right hand corner.
Select the Form that you want to make changes to from the list.
You can now make any changes that are required, such as renaming the Form or changing the Form Fields.
See the help page on Creating Forms for more details on how to change Form configuration.
Once you have made all your changes, click Save & Share. The Form will immediately be updated.
The Form link will remain fixed, even if you change the Form configuration. If you make changes to a Form that has been shared, remember that these changes will show as soon as you save the changes to the Form.